Various means have been devised to electrically adjust vehicle mirrors. Generally one or more electric motors are connected to a mirror casing for independently pivoting the casing about a horizontal axis and a vertical axis. Illustrations of various adjusting means are found in U.S. Pat. Nos. 3,609,014, 3,972,597, 4,056,253, 4,324,454, German Pat. No. 2,840,789, and European patent application No. EP 0094856.
The mirror casing of an electrically adjustable mirror is generally mounted to a base by either a ball and socket or cross-shaft type mount which permit free pivotal movement about the horizontal and vertical axes. However, in these types of mounts little attention is given to pivotal movement about a third axis which is mutually perpendicular to the horizontal and vertical axes. Additional illustrations of mounting means are found in U.S. Pat. Nos. 3,549,243 and 3,917,212.
It is important to control the amount of pivotal movement of the mirror case about the third axis, that is, an axis substantially parallel to the longitudinal axis of the vehicle. Excessive freedom of movement about the third axis causes unacceptable vibration of the image and interferes with proper adjustment and control of mirror position. Conversely, vibration problems are also created by mounting the mirror casing to the base member such that pivotal movement about the third axis is completely prevented. Since the mirror casing is generally mounted upon an arm which extends to the side of the vehicle, road or engine-induced vibrations caused by the vehicle tend to be magnified at the mirror casing. Thus, both insufficient and excessive freedom of mirror movement about the third axis are undesirable.
It is therefore an object of this invention to provide an improved means for mounting the mirror casing to the base member which avoids the aforementioned problems. In this regard, a mounting means is provided that allows a predetermined limited amount of pivotal movement about the third axis. This limited movement is just enough to prevent any vision impairing vibrations from occurring in the mirror casing, but is not enough to require the mirror to be adjusted about the third axis. The mounting means comprises a slotted ball which is pivotally received in a spherical socket having a pair of longitudinal ribs which engage the slots in the ball.
As with all vehicle mirrors, it is usually necessary to adjust mirror position for a different driver or when the driver changes the seat position. This problem occurs, for example, when an operator adjusts the mirror for himself and it is thereafter adjusted by a second operator. When the first operator wants to operate the vehicle again he must readjust the mirrors. Typically, the mirrors of a family car may frequently be re-adjusted between two alternate positions each time the driver changes.
It is therefore another object of this invention to provide an automatic return means for a vehicle mirror, whereby the mirror will automatically return to one of two or more pre-set positions without the need for the usual trial and error adjustment technique. It is desirable that the adjustment of the mirror be extremely accurate, otherwise further adjustment would be required. It is also desirable to have a reliable system which is not prone to defects, but which is readily repairable if defects do occur.
An automatic return means for an adjustable mirror has been previously attempted. The automatic return means involved a string attached to the underside of a mirror casing. The string was wrapped around a rotary drum potentiometer and a pulley. When the glass case was pivoted to a new position the rotary drum potentiometer would create a position-responsive electrical signal due to the string's travel.
The rotary drum potentiometer and pulley system had several drawbacks, including insufficient accuracy or repeatability to eliminate the need for adjustment, and breakage and loosening problems with the string and pulley system. See also U.S. Pat. No. 4,477,874.
The present invention overcomes these drawbacks by using a pair of linear potentiometers. Each linear potentiometer comprises a shaft or elongated member with one end pivotally connected to the movable mirror casing and with the opposite end being free to reciprocate in the fixed mirror base. The member carries an electrical contact which reciprocates along a conductor in response to mirror movement. This reciprocal action forms a linear potentiometer which creates an electrical signal which is distinct for each horizontal and vertical position of the mirror.
By using a microprocessor the signal generated by the linear potentiometer at a pre-set mirror position can be recorded. When the mirror is to be adjusted to a prior recorded position the microprocessor is activated. The microprocessor energizes the electric motors which pivot the mirror until the linear potentiometer generates a signal equal to the recorded signal corresponding to the pre-set mirror position. When the recorded signal is sensed the microprocessor stops the motor means.
The linear potentiometers of this invention provide the high degree of accuracy and durability required for a memory positioned mirror.